O'Hara M D, Rowley R, Arnold S B, Boyer J W, Leeper D B
Department of Radiation Oncology and Nuclear Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
Radiat Res. 1990 May;122(2):149-54.
A detailed understanding of how bone marrow stem cell progenitors are affected by heat is prerequisite to predicting how whole-body or regional hyperthermia protocols may affect bone marrow function. This investigation reports the reproductive integrity of murine tibial bone marrow granulocyte-macrophage colony-forming units (CFU-GM) after in situ hyperthermia. Heat was applied by water bath immersion of the leg of male BALB/c mice anesthetized with 90 mg/kg pentobarbital given subcutaneously. Tibial and rectal temperatures were monitored in representative animals by microthermocouples (tip diameter approximately 100 microns). By approximately 3 min after immersion of the limb, marrow temperature was within 0.3 degree C of water bath temperature (O'Hara et al., Int. J. Hyperthermia 5, 589-601, 1989) and was within 0.1 degree C by 5 min after immersion. The CFU-GM were cultured in "lung-conditioned" McCoy's 5A medium supplemented with 15% fetal calf serum and 0.3% Bacto agar. In situ heating of tibial marrow to exposure temperatures of 42, 42.5, 43, 44, and 45 degrees C gave D0's (+/- 95% CI) of 91 +/- 44, 44 +/- 27, 27 +/- 2.2, 16 +/- 6, and 7 +/- 4 min, respectively. Heating to 41.5 degrees C for up to 180 min did not result in cytotoxicity. Development of thermotolerance after approximately 100 min of heating was apparent by the presence of a "resistant tail" of the 42 degrees C survival curve. A plot of D0 vs water bath temperature was bimodal with an inflection point at approximately 42.5 degrees C. The inactivation enthalpy for temperatures above 42.5 degrees C was 586 kJ/mol (140 kcal/mol) and for temperatures below 42.5 degrees C was estimated to be 1205 kJ/mol (288 kcal/mol). These results show that CFU-GM can be heated predictably in situ, can be inactivated with thermal exposures as low as 42 degrees C, and are capable of developing thermotolerance. These findings underscore the necessity to understand stem cell inactivation by hyperthermia in situ prior to widespread implementation of clinical hyperthermia protocols where bone marrow may be included in the treatment field.
详细了解骨髓干细胞祖细胞如何受热影响，是预测全身或局部热疗方案如何影响骨髓功能的前提条件。本研究报告了原位热疗后小鼠胫骨骨髓粒细胞 - 巨噬细胞集落形成单位（CFU - GM）的生殖完整性。通过将皮下注射90mg/kg戊巴比妥麻醉的雄性BALB/c小鼠的腿部浸入水浴来施加热量。通过微热电偶（尖端直径约100微米）监测代表性动物的胫骨和直肠温度。肢体浸入后约3分钟，骨髓温度与水浴温度相差0.3℃以内（奥哈拉等人，《国际热疗杂志》5，589 - 601，1989），浸入后5分钟内相差0.1℃以内。CFU - GM在补充有15%胎牛血清和0.3%细菌琼脂的“肺条件” McCoy's 5A培养基中培养。将胫骨骨髓原位加热至42、42.5、43、44和45℃的暴露温度，其D0值（±95%置信区间）分别为91±44、44±27、27±2.2、16±6和7±4分钟。加热至41.5℃长达180分钟未导致细胞毒性。加热约100分钟后热耐受性的发展通过42℃存活曲线的“抗性尾部”得以体现。D0与水浴温度的关系图呈双峰状，拐点约在42.5℃。42.5℃以上温度的失活焓为586kJ/mol（140kcal/mol），42.5℃以下温度的失活焓估计为1205kJ/mol（288kcal/mol）。这些结果表明，CFU - GM可在原位进行可预测的加热，在低至42℃的热暴露下可被灭活，并且能够产生热耐受性。这些发现强调了在广泛实施可能将骨髓纳入治疗区域的临床热疗方案之前，了解原位热疗对干细胞灭活作用的必要性。
